The present invention relates to an instrument panel for a motor vehicle, for example, a passenger car. The instrument panel has a shell-type support preform and a covering which is integrated in the support preform. The covering is adapted to close a passage opening for a front passenger air bag. In the event of a sudden expansion of the front passenger air bag, the cover detaches, at least partially, from the support preform. The covering is connected with the support preform by means of several webs distributed along the circumference of the covering. The webs are positioned outside the contour of the passage opening.
A previously known type of instrument panel is disclosed in German Patent Document DE 43 11 241 C1. This instrument panel has a shell-shaped support preform which is made of a fiber-reinforced plastic material. The preform extends along the whole width of the vehicle interior and on a front passenger side, a covering is integrated for a passage opening of a front passenger air bag. The covering is integrally connected by way of webs with the support preform. The webs are situated outside the contour of a passage opening for expansion of the front passenger air bag. In this case, corresponding recesses are provided on an edge of the support preform which flanks the passage opening, into which recesses the webs project and on whose base the webs change into the support preform. The webs each have the same width along their whole length. In the event of a sudden expansion of the front passenger air bag, the covering is pressed to the outside, whereby the webs break off. However, it is also possible that, during such an expansion of the front passenger air bag, the webs may break off on the covering. In this case web particles or pieces remaining on the edge of the support preform may damage the expanding front passenger air bag.
It is an object of the invention to provide an instrument panel of the above-mentioned type which reliably prevents damage to the front passenger air bag in the event of a sudden unfolding.
This and other objects are achieved in the present invention by reducing the wall thickness of the support preform at least in sections in the area of the webs. The present invention provides a covering in one piece together with the shell-type support preform. As the result of reducing the wall thickness, at least in sections in the area of the webs, the material is weakened. When the air bag is expanded and the covering is pressed open, the webs necessarily and reliably break in these areas of reduced wall thickness. Since the webs, and therefore also the areas with reduced wall thickness, are situated outside the contour of the passage opening for the front passenger air bag, damage to the front passenger air bag by remaining pieces of the broken webs is avoided. The areas with the reduced wall thickness therefore form defined desired breaking points. Since the covering is integrated in the support preform and is therefore produced in one piece with the support preform, the covering always has the same wall thickness as the support preform.
According to another aspect of the invention the reduction of the wall thickness is formed by a linear transition area. As a result, weakening of the material is ensured and thus the desired breaking point is formed in a defined manner in the area of the reduced wall thickness.
According to a further aspect of the invention, the wall thickness of the support preform is reduced in a surrounding ring area, which encloses the covering and accommodates the webs. As the result of the thinner design of the surrounding ring area, the area with the reduced wall thickness can be produced with particular ease, this area being produced together with the manufacturing of the support preform and the covering in one operation. The support preform, including the covering, may be produced of a fiber-reinforced plastic material, preferably of PVC/ABS.
According to a further aspect of the invention, the webs may be formed by connection areas which taper from the covering toward the edge of the support preform. This design further improves the creation of defined desired breaking points outside the contour of the passage opening. The desired breaking point is situated in the narrowest section of each web and therefore in each case at a point away from the covering. Even considered by itself, this solution achieves the above-mentioned object.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.